148 



PLANT BREEDING 



of mutation is so ne\v_ that we do not know how mnch we are 

 indebted to it for valuable economic plants. Some of our valu- 

 able plants which we have considered the results of selection 

 niav r(\i]ly be the results of mutation. 



Hybridization is the production of new varieties (hybrids) 

 by the cross fertilization of more or less closely related species. 

 This process no doubt occurs to some extent in nature, but man 

 has taken advantage of the possibilities of this method of secur- 

 ing new and valuable varieties and many men are now devoting 

 their time to this very important line of work. The method is 



Fig. 92. — In croesing different varieties of wheat the stamens are removed before they 

 shed their pollen. Tlie pistils are impregnated with pollen brought by a soft brusti troui 

 another variety. The head is then covered with a paper bag and properly labeled. tU.S.D.A.) 



not difficult but I'equires care, time and patience. The pollen 

 can be readily collected in a watch glass or other small receptacle 

 and then applied to the stigmas of the flowers of the other plants 

 with a delicate camel's hair brnsh. The stamens of the opening 

 flowers should be removed, the pollen applied to the stigma and 

 the blossom then protected against accidental pollination from 

 other sources by covering with a paper bag. (Frontispiece.) 

 After a few days the bag can be removed and a tag fastened to 

 the shoot. In growing annual plants, the results of cross breed- 

 ing can be determined in a comparatively short time, but in the 

 cross-breeding perennials the time will be much longer unless 



